1988-04-11_PERMIT FILE - C1981008A (23)

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Both the Nucla Mine and Nucla East mining areas are located in a climate which generates less than 15 inches of precipitation annually. Evapotranspiration rates in the vicinity are relatively high (see Tab 7, Hydrologic Description). Textural analyses performed on potential spoil materials generally indicates that sandy clay loam materials will be replaced in the pits (see Tab 6, Geology). Consequently, infiltration rates in reclaimed areas are expected to be slow to moderate. It follows that contributions to spoil resaturation and subsequent recharge to surrounding aquifers from precipitation will be slow. However, the upland and adjacent irrigation ditches and laterals will eventually provide a more rapid source of recharge to spoils. Seepage from the irrigation network has provided an artificial source of recharge to the undisturbed shallow ground water system. The resaturation and recharge of replaced spoils will also be augmented by the irrigation. Overburden and topsoil handling, reconditioning, and revegetation methods outlined in Tabs 21 (Minesoil Reconstruction) and 22 (Revegetation Plan) will maximize the potential for establishing reclaimed areas that will exhibit infiltration rates and capacities adequate for insuring at least premining rates and capacities. Timely reseeding and mulching of redistributed topsoil will augment the retention and eventual downward infiltration of soil moisture. Textures of topsoil material will generally range from sandy loam to loam, and topsoil material will exhibit moderate infiltration rates. Deep ripping of regraded spoil, followed by topsoil placement, chisel plowing, and disking will improve the infiltration potential of the reclaimed medium. Significant ground water inflow to the pits will be removed by pumping the water to those sediment ponds that will, at the time of pumping, have a sufficient available storage capacity, including the prescribed volume for the 10-year, 24-hour storm. Design criteria for the ponds is addressed in Tab 13 (Facilities), and includes plans for storage of additional volumes pumped from pits or sumps. Maintenance of available storage capacity in the ponds involves dewatering and sediment removal. Ground Water Monitoring. Since 1979, Peabody has progressively installed an extensive network of 35 wells to monitor the shallow aquifers beneath both the Nucla Mine and the Nucla East mining area. Monitoring instrumentation, parameters monitored, and monitoring frequencies are described in detail in Tab 15, Hydrologic Monitoring Program. The ground water monitoring plan employed to monitor the extent and magnitude of any mining impacts is also discussed in detail in Tab 18, Hydrologic Reclamation Plan. 16-3 Revised 04/11/88